Reference is hereby made to the Microfiche Appendix "A" forming a portion of this specification and containing 1 microfiche and a total of 32 frames.
This invention is directed to a multiple device control apparatus for a multiple inputted load apparatus and particularly to a step-type controller for a water heater or like load means having a plurality of selectively actuated heating elements.
Multiple input apparatus may include a plurality of individual actuated load inputs for controlling the state of or conditioning the load apparatus by sequential and selective actuation of such plurality of inputs. For example, water heating apparatus may be constructed with a plurality of individual heating elements or units rather than one single modulated element for varying the thermal energy inputted into the stored water. The heat input may be conveniently controlled by varying of the number of the heating elements which are activated at any given time. The actuation of the heating elements may be varied depending upon the temperature of the stored water, the time of day, the anticipated usage, the recovery rate requirements and any other factor or condition which can effect the heat input requirement. In such a system, it may be desirable to provide for particular types of sequential operations of the load devices. This in turn requires proper sensing and monitoring of status of all such load input devices as well as the various control factors, and then controlling the load or element activations in accordance with the predetermined relative sensed and monitored conditions.
A step-type controller for a load having a plurality of individual inputs which are to be individually and separately activated in a predetermined sequence based on a plurality of different load and operating factors is shown in the recently issued U.S. Pat. No. 4,333,002 of the one inventor. The controller includes a microprocessor unit coupled to periodically sense the conditions of the sensors and signal sources as well as monitoring and storing the on-off status of each of the heating elements. The historical sequence of when each heating element was turned on or off in relationship to all of the other heating elements is particularly monitored. The microprocessor periodically updates the status by processing of the last read and stored signals to develop the difference between the actual and desired water temperatures, dividing the same by the span setting signal to provide for a predetermined acceptable variation and adding a constant to produce a number corresponding to the number of elements which should be in an activated state for that condition. Such number is compared with the actual number of elements then on, and if there are any deviations, appropriate control signals are generated to increase or decrease the number of activated elements to the predetermined and preset number for that temperature condition. The logic unit can readily store the sequence of the first on and the first off heating element and when required turn off the load which was first on, and turn on the load element which was the first off.